(a) Field of the Invention
The present invention relates to a liquid crystal display and a driving method thereof.
(b) Description of the Related Art
Liquid crystal displays (LCDs) are the most commonly used one of flat panel displays (FPDs) handy to carry.
An LCD includes a pair of panels having field-generating electrodes and polarizers, and a liquid crystal (LC) layer with dielectric anisotropy, which is interposed between the panels and subject to electric field generated by the electrodes. The variation of the field strength changes molecular orientations of the LC layer, which tend to align parallel or perpendicular to the field direction. The LCD passes light through the LC layer via the polarizers and reorients the LC molecules to change the polarization of the light. The polarizers convert the change of the polarization into the change of the light transmittance and enable to obtain desired images.
The LCD has a narrow viewing angle. In particular, a twisted-nematic (TN) mode LCD having nematic LC with twisted alignment is widely used due to its many advantages, its application to monitors and television sets is limited due to its narrow viewing angle.
Several techniques such as multi-domains and compensation films for widening the viewing angle of the LCD are developed. In particular, compensation films often called wide viewing films give viewing characteristics in a lateral direction as good as other wide viewing techniques. However, gray inversion (that the brightness decreases as the gray voltage increases in a normally black mode LCD or vice versa in a normally white mode LCD) in a vertical direction still remains, which is severe particularly when viewing from the bottom.
Furthermore, a multi-domain LCD shows poor visibility at a lateral view compared with a normal TN mode LCD due to the inconsistency of gamma curves for a lateral view and for a front view. For example, a patterned-vertically-aligned (PVA) mode LCD having cutouts for forming domains displays brighter and whiter images as it goes away from the front to the lateral side. Sometimes, the brightness of the higher grays becomes indistinguishable to make the image mashed.